Beryllium alloys



United States Patent 3,145,098 llERYLLlllJh/i ALLOYS Thomas Raine, lltramhall, and James Alan Robinson, Cheadle, England, assiguors to Associated Electrical industries Limited, London, England, a British company No Drawing. Filed .iune 7, 1062, Ser. No. 200,633 Claims priority, application Great Britain June 27, 1961 3 Claims. (Cl. 75-150) This invention relates to alloys suitable for use at high temperatures in an atmosphere of carbon dioxide. Such conditions arise in the core of graphite-moderated advanced gas cooled nuclear reactors in which carbon dioxide is used for cooling and heat extraction and where metallic parts are in contact with the hot gas. Because of its extremely low neutron cross-section consideration has been given to the use of beryllium as a fuel containment material to protect the fuel from oxidation by the cooling gas and to promote eflicient heat exchange between the fuel and the gas.

The oxidation resistance of commercially produced reactor grade" beryllium is very good at elevated temperatures in air, but in pressured carbon dioxide the corrosion resistance in the temperature range 650 C. to 700 C. is very poor. Assessment of the degree of corrosion is difficult because oxidation occurs at randomly distributed areas on the surface due to local unavoidable impurities; these areas resemble blisters.

In co-pending application Serial No. 144,312, filed on October 11, 1961, by us and assigned to the assignee of the present application, we have proposed to increase the resistance to corrosion of beryllium to moist hot carbon dioxide by alloying with the beryllium 0.05% to 3.0%, by weight, of calcium. The addition of calcium to the beryllium does not materially affect the neutron transparency of the alloy.

The object of the present invention is to provide beryllium base alloys which, while possessing adequate resistance to corrosion and high neutron transparency, have improved mechanical properties over the binary beryllium-calcium alloy above-mentioned.

We have found that when beryllium is alloyed with any one of zirconium, niobium, vanadium and titanium, in addition to the calcium specified in the aforesaid specification to provide a ternary alloy, the resulting alloy has a greater strength than the binary beryllium-calcium alloy.

The invention accordingly consists of a ternary alloy of beryllium with 0.1% to 3%, by weight, of calcium, and with 0.1% to 2.0%, by weight, of a metal selected from the group consisting of zirconium, niobium, vanadium, or titanium.

The content of calcium in the ternary alloy is preferably 1.0%, by Weight, or more up to the limit of 3.0%, while the content of the additional element is preferably about 0.5%, by weight.

These formulations imply within the content of beryllium the inclusion of the unavoidable impurities present in reactor grade beryllium.

The advantage of the ternary addition lies in the higher strength of the ternary alloy compared with the base binary beryllium-calcium alloy. This improved strength is achieved with only a marginal decrease in the corrosion resistance and without affecting the basic mechanism of corrosion protection afforded by the calcium addition.

Results of mechanical tests at 600 C. show that the 3,145,098 Patented Aug. 18, 1964 ternary alloys have much greater strength than the binary alloys without a significant loss in ductility, e.g.,

Limit of Ultimate Percent Percent Room temperature hardness tests show hardness values varying from to V.P.N. for the binary alloys and from 200 to 230 V.P.N. for the ternary alloys.

The decrease in corrosion resistance of the ternary alloys, as compared with the binary alloys is exemplified by the following particulars of tests carried out. After 4-300 hours exposure at 700 C. in carbon dioxide at 300 p.s.i.g. pressure containing 300 ppm. H O, the weight gain of a binary 0.56% calcium alloy was 0.286 mg./cm. After the same time and under the same conditions the Weight gain of a beryllium 0.54% calcium-0.5% zirconium alloy was 0.746 mg./cm. In both cases the rate of corrosion was decelerating with exposure time, i.e., a protective oxide layer was formed. Results for ternary alloys containing titanium, niobium or vanadium in place of the zirconium in the above example were almost iden tical. By the addition of excess calcium, i.e., in the above case 1.0% total instead of 0.54% the corrosion behaviour of the ternary alloy is identical to that of the 0.56% calcium binary alloy mentioned above.

The ternary alloys can be made by any of the conventional powder metallurgical techniques. However, a preferred process comprises consumable-electrode arc melting followed by direct fabrication, i.e., extrusion of ingot to tube, or rod, etc., or by forging and rolling to sheet.

The choice of fabrication process does not affect the improvement in corrosion resistance by any significant amount.

All the tests above referred to were carried out on billets produced by are melting in vacuo. All results are for are melted and directly fabricated material with an oxygen content of about 200 ppm. weight.

What we claim is:

1. A corrosion resistant beryllium-base alloy consisting of 0.1% to 3%, by weight, of calcium, 0.1% to 2%, by weight, of a metal selected from the group consisting of zirconium, niobium, vanadium and titanium, and remainder beryllium including unavoidable impurities.

2. A corrosion resistant beryllium-base alloy consisting of 1.0% to 3%, by weight, of calcium, 0.5%, by weight, of a metal selected from the group consisting of zirconium, niobium, vanadium and titanium, and remainder beryllium including unavoidable impurities.

3. A corrosion resistant beryllium-base alloy consisting of 1%, by weight, of calcium, 0.5%, by weight, of a metal selected from the group consisting of zirconium, niobium, vanadium and titanium, and remainder beryllium including unavoidable impurities.

Kaufmann et al.: The Metallurgy of Beryllium, Transactions of the American Society of Metals, vol. 42, 1950, pages 801 and 840. 

1. A CORROSION RESISTANT BERYLLIUM-BASE ALLOY CONSISTING OF 0.1% TO 3%, BY WEIGHT, OF CALCIUM, 0.1% TO 2%, BY WEIGHT, OF A METAL SELECTED FROM THE GROUP CONSISTING OF ZIRCOONIUM, NIOBIUM, VANADIUM AND TITANIUM, AND REMAINDER BERYLLIUM INCLUDING UNAVOIDABLE IMPURITIES. 